The long-term objective of this study is to understand the role of the nervous system in the regulation of endocrine organs. This will be accomplished by investigating the physiological regulation of juvenile hormone (JH) synthesis by the corpora allata (CA) in developing cockroaches, specifically the embryonic and larval stages of Diploptera punctata. The specific aims are to: 1) isolate and characterize the peptide(s) from the brain that function in neural and humoral inhibition of the CA in the larva, 2) localize their cellular source and release sites, 3) demonstrate the factors that promote their release from the nervous system, and 4) study the effect of the neuropeptides on the CA at the cellular level. Both sexes will be studied throughout development with the aim of learning when and how male and female CA undergo their physiologically distinct sexual differentiation. Neuropeptides will be isolated by high performance liquid chromatography (HPLC) separation of brain extracts. Active inhibitory fractions will be determined by a rapid in vitro radiochemical assay. Monoclonal antibodies to the neuropeptides in active fractions will be generated and used as histological probes to localize the source and release sites of the active peptides. To confirm their identity, the antibodies will also be tested for their ability to block the action of the inhibitory factors on the CA in vivo and in vitro. Potential releasing factors for the inhibitory neuropeptide, such as JH, 20-hydroxyecdysone, and neurotransmitters, will be tested in vivo and in vitro. The effects of the neuropeptide(s) on concentrations of cyclic nucleotides, activity of methyl transferase (in the penultimate step of JH synthesis), and qualitative and quantitative changes in the fine structure of intracellular organelles in the CA will be studied. Experimental procedures will include denervation and transplantation of CA and decapitation of hosts.